Bone regeneration after alveolar dehiscence due to orthodontic tooth movement – A case report

INTRODUCTION

While performing non-extraction orthodontic therapy, there is an inevitable tendency to procline the lower incisors. While not ideal, it is usually regarded as an acceptable compromise when camouflaging skeletal base discrepancies.^[1] To minimize proclination, buccal root torque can be added to the archwire. This case report shows the sequelae of excessive lower incisor torque using a customized appliance and the long-term results after correction. An anterior negative 20-degree pre-torqued 19×25 NiTi wire was placed in the lower arch and the patient did not return for 3 months. This resulted in the apices of the anterior lower incisors being placed outside the alveolar housing. To correct this, the wire was then flipped and reinserted to obtain positive torque. After 4 months, the roots were back within the alveolar bone according to cephalometry. Four years after treatment, a cone-beam computed tomography (CBCT) scan indicated that there was normal and adequate bone covering of the lower incisor roots with no sign of any adverse effects.

Animal studies^[2-5] have previously reported that the occurrence of bone reapposition after teeth was initially expanded through the cortical plate and then returned toward their normal positions in the arch. Wainwright,^[2] Karring et al.,^[3] Engelking and Zachrisson,^[4] and Thilander et al.^[5] all concluded that dehiscence or fenestrations can be produced in the buccal alveolar plate by moving teeth in a facial direction and that the bone will reform when the teeth are moved back toward their original positions. Only Engelking and Zachrisson^[4] showed gingival recession after dehiscence or fenestration formation, which was also not recovered after moving the teeth back to their original positions.

A case report by Pazera et al.^[6] showed a deformed lower fixed retainer causing approximately 35 degrees of buccal root torque of the lower right canine. A CBCT showed the apex of the tooth outside of the cortical bone; however, the tooth was vital and had only mild recession. The patient was then retreated orthodontically and a new CBCT was taken before debonding. They found minor bone regeneration around the apical and buccal surfaces.

CASE REPORT

A 15-year-old male patient presented for orthodontic treatment for the correction of crowding. Extraoral examination showed a convex profile with lip incompetence, increased lower facial height, and a flat smile arc. Intraoral examination exhibited a Class I molar and canine relationship, 2 mm overjet, and 1 mm overbite. Both upper and lower arches were asymmetrical with a collapse in the buccal segments of the 2^nd and 3^rd quadrants resulting in scissor bites of the upper left 2^nd premolar and 2^nd molar. Crowding of 2 mm in the upper arch and 6.5 mm in the lower arch was found. A Bolton discrepancy with excess tooth material in the lower arch was present (1.7 mm anterior and 7 mm total) [Figure 1].

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Figure 1

Initial records of the patient.

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A panoramic radiograph showed that all teeth were present with potentially impacted 3^rd molar. Cephalometric examination indicated a skeletal Class II relationship with a mild dolichofacial pattern and proclined and protruded upper and lower incisors [Figure 2 and Table 1].

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Figure 2

(a and b) Initial radiographic records. Note the presence of the third molars, the mild vertical pattern, and the proclination of upper and lower incisors.

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Treatment goals involved resolving upper and lower crowding, correcting the teeth in scissor bite, maintaining Class I occlusion, and improving smile esthetics.

Treatment options included extraction and non-extraction treatment; however, a non-extraction plan was agreed on, using a customized appliance (Insignia^) with low torque compensations in the customized brackets (labial root torque) and lower interproximal stripping and intermaxillary elastics [Figure 3].

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Figure 3

T1 and T2, approver program from Insignia^, showing the correction of Class II with intermaxillary elastics.

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Treatment proceeded first with a 14 CuNiTi archwire in the upper and lower arches (5 months), followed by 14×25 CuNiTi (5 months, with Class II elastics used on the left), 18×25 CuNiTi (1.5 months – Class II elastics on left), 19×25 TMA (3 months – bilateral Class II elastics), and 19×25 NiTi with 20 degrees buccal root torque to upright incisors. The patient did not attend his appointment until 3 months later.

On his return, a cephalometric radiograph was taken which showed that the apex of one of the lower incisors was completely out of the alveolar bone [Figure 4]. Clinically, it appeared that the lower right lateral incisor was the tooth affected, although there were minimal signs of gingival recession and all teeth were vital [Figure 5]. The 19×25 NiTi with 20 degrees torque was then flipped to express positive torque (lingual root torque) for 4 months.

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Figure 4

Lateral cephalometry showing the apex of the lower incisor completely out of the alveolar bone due to the excessive negative torque in the archwire.

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Figure 5

Clinical view of the affected lower right lateral incisor showing minimal signs of gingival recession, despite the apex being out of the cortical bone.

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Finishing was performed using 19×25 TMA and treatment completed in 21 months with fixed retainers placed from 3 to 3 in the upper and lower arches [Figure 6]. There appeared to be no visible adverse effects on the periodontium. A cephalometric radiograph taken at debonding showed the roots of the lower incisors within the alveolar housing [Figure 7].

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Figure 6

Final records of the patient. The treatment was completed in 21 months using Insignia^

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Figure 7

Final cephalometry showing the roots of the lower incisors within the alveolar bone.

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A panoramic radiograph taken at debonding showed acceptable root angulations, no evidence of root resorption, and stable bone levels. The radiograph did reveal impaction of the lower left ^3rd molar [Figure 8]. Cephalometric superimposition [Figure 9] showed reduced upper and lower incisor proclination, resulting in an increased interincisal angle.

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Figure 8

Final panoramic radiograph showing acceptable root angulations, no evidence of root resorption or alveolar bone loss and an impacted lower left 3^rd molar.

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Figure 9

Superimpositions showing the increase of the interincisal angle.

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The patient returned after 4 years post-treatment with a stable occlusion despite debonding and loss of the lower fixed retainer [Figure 10]. Clinical assessment showed that the periodontium around the lower incisors was healthy, and a CBCT (Kavo OP 3D, 5 cm×5 cm, 85 µ) was taken to further asses the status of the lower incisors. The CBCT showed good bone coverage of the roots with no apparent adverse effects from the orthodontic treatment [Figure 11].

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Figure 10

Four years post-treatment records, with stable occlusion and a healthy periodontium around the lower incisors.

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Figure 11

(a-c) Cone-beam computed tomography 4 years post-treatment showing normal coverage with no apparent adverse effects from the orthodontic treatment.

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DISCUSSION

The patient in this report had severe dehiscence of the lower incisors, but surprisingly no apparent periodontal pathology. Merely placing the roots back into the alveolar bone resulted in a favorable long-term result. The question arises that if there were periodontal issues, would the same treatment be effective? According to Engelking and Zachrisson,^[4] it would not. Therefore, if periodontal pathology was present, it would likely be better to also perform a bone and connective tissue graft. According to Mandelaris et al.,^[7] a pre-treatment CBCT could improve prediction of alveolar bone changes caused by orthodontic tooth movement and can influence periodontal decision-making if lower incisor protrusion is initially predicted, especially in hyperdivergent patients.^[8,9] In such a case, periodontally accelerated osteogenic orthodontics could be performed initially to increase the scope of treatment.^[10,11]

CONCLUSION

Orthodontists should be aware of possible complications of excessively torquing lower incisors to prevent proclination. Although permanent damage could occur, it is imperative to note that a good long-term prognosis is possible using orthodontics alone, especially if there is no gingival pathology.